There is a lack of non-invasive devices capable of performing fast, repeated measurements of blood pressures features such as the diastolic blood pressure, the mean blood pressure and the systolic blood pressure. Known devices may either be too complex, too expensive, too slow or inaccurate in order to be usable for certain purposes.
One purpose of such a blood pressure measurement device is for use with cardio pulmonary resuscitation (CPR) applied to a cardiac arrest victim where certain features of blood pressure measurements may be useful for assessing the quality of the CPR. Having repeated fast measurements allows for multiple assessments of CPR quality in a certain time frame.
Such blood pressure measurements might also be used to assess whether CPR was effective in restoring the subject's own heartbeat. Detection of the presence of a life sustaining pulse is a key action in determining if a subject's heart is beating spontaneously, and therefore if CPR has been successful. The point at which the heart starts to spontaneously generate life-sustaining blood flows again is known as the return of spontaneous circulation (ROSC). Determining ROSC is usually done by pausing CPR and performing manual palpation. However; this process is time-consuming and the resulting interruptions can negatively impact the outcome of the CPR. High-quality CPR requires minimizing interruptions to the chest compressions. Furthermore, manual palpation is known to be unreliable even if performed by expert clinicians, and even when a pulse is present it is often very difficult to determine if it is life sustaining. Monitoring of end-tidal CO2, invasive blood pressure, or central venous oxygen saturation allows for a more objective assessment of ROSC, but are invasive as all require a secured airway or the placement of catheters. Trans-thoracic impedance (TTI) measurements and near-infrared spectroscopy (NIRS) are non-invasive, but TTI is strongly influenced by chest compressions and NIRS responds slowly upon ROSC. It would therefore be desirable to have a non-invasive, rapid and objective way of determining ROSC.
Further, trends of certain blood pressure features (e.g. diastolic, mean and systolic levels) can be used as an indicator of hemodynamic instability. Monitoring hemodynamic stability is especially important in critical and emergency care (e.g. for ICU patients and patients undergoing surgery or resucitation). A (semi-)continous time series of at least one pulse pressure feature is necessary to ensure hemodynamic stability, or to detect deterioration. Currently hemodynamic stability has to be measured using invasive blood pressure catheters or using devices that cannot measure absolute pressures.
Accordingly there is a need for a non-invasive blood pressure measurement device capable of (semi-)continuously measuring blood pressure features such as the diastolic, mean and systolic blood pressures. Preferably, such a device would also be capable of performing fast and accurate tracking and measurements of blood pressure features.
US2010/0094140 discloses a method to measure intravascular or other compartment pressure by applying extrinsic pressure oscillations. Pressure-volume response of the compressed structure is obtained and compartment pressure is estimated as the extrinsic pressure at which compressed structure has the highest compliance. By delivering extrinsic oscillations at a higher frequency than the pulse rate, pressure reading can be obtained much faster. Because it is not dependant on intrinsic vascular oscillations, pressure can be measured during arrhythmias, during cardiac bypass, during resuscitation, in the venous compartment or in the other non-pulsatile compressible body compartments.